CB750k not getting fuel into cylinders

Cb750gocart

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I have a 1978 Honda cb750k and I’m having troubles with the carburetors. I am getting fuel into the bowls but there is nothing getting into the cylinders. Carburetor number 1 is just running out of the overflow. It fires right up on starting fluid but not getting fuel into cylinder. Do the run off of vacume or something? Btw the motor is completely mounted in a gocart frame and everything is done just waiting to figure out the carb issue! Thanks for your time!
 

dirtdigger

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If the bowls are full then it has to be plugged jets or passages no other way around it. Unless the engine has zero compression and producing no vacuum to draw air/fuel in but that really cant be if it will fire up on starter fluid. Have you actually verified that you have an appropriate float level? Fuel running out of the over flow indicates either too high level, stuck float or a float that doesnt float. Have you verified open passages by blowing air through them? Just because they have been "cleaned" doesnt actually mean they are clean. Also are these stock carbs??
 

amc49

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If OP is posting in '87 forum I suggest a pic of carb to be sure of what is what here.

That does not affect post #11 which is 100% correct.
 

Cb750gocart

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If the bowls are full then it has to be plugged jets or passages no other way around it. Unless the engine has zero compression and producing no vacuum to draw air/fuel in but that really cant be if it will fire up on starter fluid. Have you actually verified that you have an appropriate float level? Fuel running out of the over flow indicates either too high level, stuck float or a float that doesnt float. Have you verified open passages by blowing air through them? Just because they have been "cleaned" doesnt actually mean they are clean. Also are these stock carbs??


Yes they are stock carbs. I will run through them again. Not sure what else to do though. Where is it’s path between the bowl and the cylinder? How do I adjust float height?
 

dirtdigger

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Sounds like you know little to nothing about how engines function. I normally dont tell people to not attempt something but you need to take this to someone that knows what they are doing unless you have the time and patience to learn. First you need a honda shop manual so you can see the procedures and do some learning. These are simple carbs but if you dont know how fuel gets from the bowl into the engine then this is something you probably shouldn't attempt.
 

Cb750gocart

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Sounds like you know little to nothing about how engines function. I normally dont tell people to not attempt something but you need to take this to someone that knows what they are doing unless you have the time and patience to learn. First you need a honda shop manual so you can see the procedures and do some learning. These are simple carbs but if you dont know how fuel gets from the bowl into the engine then this is something you probably shouldn't attempt.

I actually do a lot of small engine work and repairs. When I said what is it’s path between the bowl and the cylinder I was meaning like is there anything special about these carbs that’s not like really any others where funk can get hung up at. Tbh with you I have probably rebuild and did a good run through on 50 carbs lol. These just really have me hung up.
 

amc49

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The work involves making sure every single little hole is known to be open and done. If you don't chase every single hole then you have wasted time, you can clean them 30 times and still not be right.

Every carb design on the planet has peculiarities. If by small engine one means like lawn equipment, those are so basic they cannot be applied to bike carbs as bike carbs have the full complement of up to 10 circuits in each carb for pathways for fuel/air and myriad calibrated holes in each. Lawn equipment being usually constant speed are much less complicated and have less circuits.

'Where is it’s path between the bowl and the cylinder?'

500 page books get written on that.
 

Cb750gocart

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Thank your for all your help. When I said smal engines I mean like 400ex, mower, dirtbike. I figured out the only problem was not having the air box on. Kinda figured it would still run without it. Quads and other bikes seem to be fine without them. Thanks for tour time!
 

dirtdigger

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It will run without the air box. You obviously inadvertently did something while putting the air box on because that makes no sense. Out of curiosity post a picture of your motor and carb setup. Something isnt right
 

amc49

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X2, my 550 runs without one and perfectly. Same engine design only smaller. Unless you have a '79 750 and those are definitely different. Need airbox to run right on those.
 
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